In many industrial electronic devices, communication devices, and the like, different power supply systems such as an AC power supply system, a DC power supply system, a telephone line system, etc., are disposed inside the same device to transmit an electrical signal.
In such a case, operations can be stable and safety can be ensured by using an optically coupled insulating device that can transmit the electrical signal in a state in which the input circuit and the output circuit are insulated from each other.
When a high voltage of 1 kV or more is applied between the input terminal and the output terminal of such an optically coupled insulating device, a noise component may occur in the light receiving element due to the electrostatic capacitance of an insulating layer between the input terminal and the output terminal.
Such noise can be reduced by covering the light receiving element with an electromagnetic shield film made of ITO (Indium Tin Oxide), a metal thin film having a mesh configuration, etc. However, it is difficult to improve the suitability for mass production of such an electromagnetic shield film in the manufacturing processes of the light receiving element.